A lot of grey areas there...hard to say. As far as the not talking goes, they really do all develop SOOOOO differently. I have a little guy who basically didn't talk at all until almost 2 and then it was very slow. He seemed to listen and observe, but now at 2 1/2 this little guys doesn't STOP talking and he used to worry me. 18 months is still young to totally react to danger also, as in being hit with drawers....and some people no matter how old are just a little slower.
Some things do sound odd, but I'd say at this point it's wait and see...